1. Field of the Invention
The present invention relates to an azeotropic composition and a cleaning method to be used for removing soils such as oils or dusts adhered to articles such as electronic components such as integrated circuits, precision (machinery) components or glass substrates.
2. Discussion of Background
To remove various oils, dusts, etc., 3,3-dichloro-1,1,1,2,2-pentafluoropropane (hereinafter referred to as R225ca), 1,3-dichloro-1,1,2,2,3-pentafluoropropane (hereinafter referred to as R225cb) or a mixture thereof (hereinafter referred to as R225), which is non-flammable, less toxic and excellent in the stability, is, for example, widely used.
However, there are certain soils which can not be removed by R225ca, R225cb and R225 (hereinafter these will generally be referred to as R225s), and the range of their application has been limited.
It is an object of the present invention to provide a solvent composition which is an azeotropic composition and which can be used in a wider range of applications, by improving the solvency for soils, while maintaining the non-flammability which is a characteristic of R225s.
As a result of an extensive study, the present inventors have found it possible to prepare an azeotropic composition by mixing R225cb and n-hexane in a specific ratio and to improve the solvency to a level higher than R225cb.
The present invention provides an azeotropic solvent composition comprising 90.3 mass % of 1,3-dichloro-1,1,2,2,3-pentafluoropropane and 9.7 mass % of n-hexane.
Further, the present invention provides a cleaning method which comprises removing soils adhered to an article by means of the above azeotropic solvent composition.
The blend compositional ratio of the azeotropic solvent composition comprising R225cb and n-hexane is R225cb/n-hexane=90.3 mass %/9.7 mass %, and the boiling point of this azeotropic composition is 55.1xc2x0 C. at 1013 hPa.
U.S. Pat. No. 5,118,438 discloses an azeotrope-like composition comprising R225cb/n-hexane=76.5 to 88.5/11.5 to 23.5 (mass %) . The present invention is based on a discovery that an azeotropic composition exists outside the compositional range of such an azeotrope-like composition. The azeotropic solvent composition comprising R225cb and n-hexane of the present invention has an advantage in that as compared with the conventional azeotrope-like composition comprising R225cb and n-hexane, there is no compositional change in the composition even if the composition is subjected to evaporation and condensation repeatedly, and an extremely stable performance can be maintained.
The solvent composition of the present invention is non-flammable and is an azeotropic composition, whereby there is no change in the composition even when it is used for vapor degreasing or repeatedly used by e.g. distillation, and it can be used in the same manner as R225cb, whereby no substantial change of the prior art is required for its use.
The azeotropic solvent composition of the present invention is useful for various applications in the same manner as the conventional R225s compositions. Specific applications include an application as a cleaning agent to remove soils adhered to an article and an application as a carrier solvent for coating various compounds or as an extracting agent. Further, as its solvency is higher than R225s, it can be used for removing soils or as a solvent or an extracting agent, in a range wider than R225s.
The azeotropic solvent composition of the present invention is particularly suitable as a cleaning agent to remove soils adhered to an article. The article to be cleaned may, for example, be made of glass, ceramics, plastic, elastomer or metal. Specifically, the article may, for example, be an electronic or electrical equipment, a precision machinery or equipment, an optical article, or a component of such an article, such as an integrated circuit, a micromotor, a relay, a bearing, an optical lens or a glass substrate.
The soils adhered to the article may, for example, be soils which are used for the manufacture of the article or components constituting the article and which must finally be removed, or soils which are adhered during the use of the article. The substance constituting the soils may, for example, be oils such as greases, mineral oils, waxes or oil-based inks, or dusts.
As a specific means to remove the soils, hand wiping, dipping, spraying, mechanical agitation, combination thereof, may, for example, be employed.
Now, the present invention will be described in further detail with reference to Examples. However, it should be understood that the present invention is by no means restricted to such specific Examples.